Aqueous humor formation is mainly a composite of ultrafiltration (dialysis in the presence of hydrostatic pressure) and active secretion by the epithelium of the processes of the ciliary body. Final aqueous humor composition is determined by both of these actions which are influenced by systemic and local metabolic, humoral, circulatory or neurologic factors. The aim of this proposal is to investigate transport processes in the isolated iris-ciliary body independent of these factors. Studies are to be performed using tissue from albino and pigmented rabbits, cats, monkeys and human autopsy eyes. Experimental technique will include the following: 1) Transepithelial measurement of tissue potential difference, short-circuit current, ionic fluxes and fluid transport to provide an overview of active transport processes. 2) Oxygen consumption studies on isolated strips of ciliary processes to measure the metabolic status of the tissue as well as the mechanism by which agents affect rates of active transport. 3) Conventional, ion specific and pH microelectrode studies to characterize the steps in ion translocation across the double epithelial layer of the ciliary processes. In vitro transepithelial and intracellular electrical measurements can provide important insights into the normal physiology and transport of this leaky epithelium. Characterization of the metabolic parameter permits evaluation of the specificity of action for drugs which affect transepithelial and intracellular electrical parameters. Pharmacological studies can give information on basic and altered states of iris-ciliary body secretory and transport processes. Agents to be investigated include (Na+,K+) ATPase inhibitors, carbonic anhydrase inhibitors, ion exchange inhibitors, adrenergic agonists and antagonists.